Hierarchical production planning systems attract today much attention of both management scientists and practitioners. Hierarchical production planning systems are often decomposed into three decision-making levels, i.e. a medium term level, a short term level, and a very short term level. This paper presents a medium term production planning model. At first, all machines which can perform the same operation are aggregated. Group technology is used to decompose the system into several subsystems, then specific attention is given on how to aggregate the subsystems. Similarly, parts are aggregated. We end up with an aggregate planning model involving production subsystems and part families.
